ASP.NET : Get Attribute Value from XML

Question

Hi Experts,

My Xml is :

<?xml version="1.0" encoding="utf-8"?>
<Sis xsi:noNamespaceSchemaLocation="Sis.xsd" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <Student>
    <StudentID>1</StudentID>
    <AcademicDetails>2008-2009</AcademicDetails>
    <PersonalDetails>
      <FirstName>Vijay</FirstName>
      <MiddleName>Laxmanrao</MiddleName>
      <LastName>Jadhav</LastName>
    </PersonalDetails>
  </Student>
</Sis>

I need to extract the value of xsi:noNamespaceSchemaLocation (ie. Sis.xsd).

How to get it ?

I have try below snippet, but it will show sXSDFile always null. Why ?

        public static bool ValidateXml(Stream oXmlStream)
        {
            string sXsdPath = "";
            string sXSDFile = "";
            try
            {
                XmlTextReader xmlTextReader = new XmlTextReader(oXmlStream);
                sXSDFile = xmlTextReader.GetAttribute("xsi:noNamespaceSchemaLocation");               
            }

            catch (Exception ex)
            {
                _isValied = false;              
            }
            return _isValied;
         }

Sample code would be greatly appreciated.

Thanks.